Directional control centrifugal blasting machine



June 27} 1944- w. A. ROSENBERGER El'AL 2,352,588;

" DIRECTIONAL CONTROL CENTRIFUGAL BLAST-ING MACHINE Filed March 7, 1941' s Sh'et s-Shgt'i w. A. ROSENBERGER ET AL 2,352,588

June 27, 1944.

DIRECTIONAL CONTROL CENI'RIFUGAL BLASTING MACHINE Filed March '7, 1941 s Sheets-Shet 2 14. 1205822 Zeqyer' Z. .Zfefer M .7122772'0 772 722M er y g Patented June 27, 1944 nmnc'rrouan oon'rnor. CENTRIFUGAL V 1 .BLASTING MACHINE Y Willia A. Rosenberg'et and .Walter 1,, Ke f v t Hagerstown, Mdg; assigners to Pangbom Cor- 'poration, Hagerstown, Md., a -corporation' ;of

Maryland Application Mai-6h 7., 1941,.'ser1a11 1o 3s2,256

Y 10 Claims. 01. s t-9 This invention relates to a directional control centrifugal blasting machine for p-ropelling at high velocity and ina desired direction'astream. of. abrasive such as steel shot, or metallic grit,

against a casting or-other object for the removal of surface'material therefrom.;

r The machine of our invention includes a; rotor driven at high speedupward of 2000 R. P. M.-, comprising a head and a plurality of substantially radially arranged propeller blades, an abrasive-supply having a discharge port located coaxial of the rotor, and a transfer mechanism between therotor'and the supply for receiving in an unobstructed axial passagethe abrasive delivered from said port and propellingit outward ina stream transversely across the orbit of the inner edges-of the propeller blades atv a selected clock-dial position,

The propeller blades function.independently! of one another and the inner edges thereof during theirpassage. through only a short selected arc successively cut off the outer portion of the abrasive stream, which is of substantially the full width of the blade,.and the severed slug of abrasive is picked up'and carried forward by, the

blade which cuts it off from the stream. Due to the centrifugal force developed in the angular movement of the blade the abrasive is caused to t'ra.vel lengthwise thereof and glides from'its outer edge at a velocity and in 'aeirection which is the. resultant of the velocity acquiredthereby in its movement with the blade andthe velocity due to centrifugal force.

Each blade is thin in the direction of its travel, or in a direction perpendicular to its carrying face to avoid the presentation .of more than an-.

inconsequential obstruction to the outward travel of the abrasive streamfrom the transfer mechanism and for avoiding the presentation of an arresting surface against which the abrasive the discharge of abrasive streams toward the, work-at an abrading velocity,-in; the rotation of the "rotor .at optimum speed; and the inner edge portions. thereof are located sufliciently closeto theaxis of rotatlonto'avoidhlgh, or destructive,

initial impact of the blades with the abrasive,

'Iheabrasive isdischarged from theouter edges ofthe rotor, blades only during their passage through a relatively short .arc, the position. of g which is relatedto and determined by the position of the short are traversed by the inner edges of the blades during which only they. pick up the abrasive, and thus the abrasive stream discharged at high velocity :from the rotor,.or the streams discharged fromthe outer "edges of the rotor blades, may-be directed to play only upon work located belowlthe' axis of the machine. or only uponwork-locatedabo've 'the, -axis of the machine, or only upon work located at intermediate points.;

Among the salient obiectsof the invention are toprovide a machine of theLcharacter recited. which is particularly simple I and strong. in construction; in which replacements may be readily made ofthe parts which are subjected to rapid.

wear; in which the faceofeach rotor blade is from the outer to the innercd'geof the blade. without abruptchange .in direction and'ls highly resistant to abrasion; in which the travel of the abrasive outwardly from the transfer mechanism is not materially arrested. or a materialarea.

presentedfor lodgment ot-"abrasive by the rotor bladesor. carrierstherefor; .in which a. guard. about theperiphery ofthe' rotor isv not required for determining the clock-dial. {P sition of the discharge ,of thestream of abrasive from the,

might lodge and act with destructive effect upon the control-member of the transfer mechanism and the blades are so supported as to ,leave wide unobstructed spaces therebetween for the free and unobstructed outwardtravel of said stream.

The front, or abrasive carrying, face of the blade is' made without abrupt change in direction from its inner to its outer'edge and this area is also made highly resistant to abrasion, and in consequence there is no material abru'ptch-angein i the direction of --trave1 of the abrasive from the rotor, or rotor blades; in which the'acceleration of the abrasive by the rotorblade is not retarded; in which the rotor blade lnllength great y fexceedsthe .radiusof the outer member for the transfer mechanism and? the inner ends-"of said blade'te'rminate inciose juxtaposition to said-out-' er member, and in which the inner member of" the transfer mechanism'includes a. plurality of radial vanes or blades having inner thin edges the abrasive supply :and permitting the unob'- structed-flow of the abrasive into and lengthwise of said passage.

A- preferred. construction- 0f machine" eirhibita; .ing our invention is illustrated in the, accompany lug-drawings wherein:- l v Figure 1 is-afront elevation of the machine;

Fig. .2 is avertical sectional viewtaken o'nthe bladeinitially contscts'the stream.

*As shown herein-the rotor comprises ahead the arrows at the ends of said line;

Fig. 3 is a sectional view taken on the line 3-4, Fig.2, looking in the direction of the ar-.

rows at the ends of the line;

Fig.4 is a sectional view taken'on theline 44, Fig. 1,[1ooking intho direction of the-arrows at the endso'f the liner Fig. 5 is a partial'front elevation of Fig. 1,

' at the feed spout, showing the arcuate retaining plate displaced below its proper position;

L 2,852,588 line 2-2 of Fig. 1, looking in the direction of -velocity to effect the desired abrading or attrition action, provided the head is rotated at an appropriate speed of the order stated for a rotor Fig. 6 is an exploded view of the wheel an d spout;

Fig. 7 is-a Fig. 8 is a section on the line of 3 of. the inner disc only of the runner head; i

Fig. 9 is a detailed sectional view taken on the front elevation of-the control shell;

line H, Fig.3, looking in the 'dir ection'of the arrows at the ends of said line;

Fig. 10 is a perspective view of one of the propellerblades. I I e, l

In general, the machinecomprises (a) a rotor,

' (b) an abrasive suppl spoutpand (c) a transfer mechanism located coaxial of the rotor which picks up'the abrasive discharged from the spout anddirects it in a-stre'am travelling forwardlyand outwardly across the orbital-path ofthe inner' end edge of each propelling blade of the rotor; and at an acute-angle to its face when the and four widely spacedapart substantially radially 'disposed propelling blades. The-blades act independently or one another in severing the outer portion of the abrasive streamxpropelled" by the transfer mechanism, and'in accelerating.

it'and in discharging it toward the workpiece; Therotor head includesan outer-circular disk I, fixedly secured to a hub l -splinedpor otherwise rigidly attached, to a horizontal shaft r driven at high speed-01 the order of 2250'revolutions. per "minute by suitable means, as

electric motor." Attached'tot'he hub 2 by screws 4 is a flat ring I whichis coaxial thereof and snuglvilts within anaxial opening in v the disk-I.

Fixedly attached to'the inner'face'of the disk Lby suitablescrews', is an innervdis h t: of; practically the same diameter disk I; and having' a like,;but somewhat larger, axial open-- ingthan that in hie-disk The second disk is provided with a plurality of radial slotsjflj'edual innuniber to numberof propeller blades ll to be hereinafter described, which o n; at their innerlxend'through' the-axial; opening therein, and areciosed at their-outer endadiacent the periphery of by an undercutwall Each blade. extends inwardly" from a point contiguous Zthe periphery of disk to "a point contiguous the periphery of the cylinder wall ,0!

'thefshell 2s ofithe transfer mechanism iatertc be described. Theiro'nt ofeach propelling blade'is oblong .111 shape and 18 without abrupt change in direction fromfend to.

end and'is initially si'ibstantiallysmooth. ,Tn

abrasive is picked up by the inner end portion of the blade with a low order'of impact, and the blade continuously accelerates the abrasive withoutzabrupt changes in the. general direction of: its movement, until it glides from the outer-edge of blade'in a stream which is uninterrupted untilit'strikesthe work; Each propelling blade is of suiiicient length to insure that the abrasive gliding oiffof its outeredge, or discharged from g the periphery c: the rotor, is as s'uiliciently high abrasive, will flow into the entrance end of the of about nineteen inches in, diameter.

Each propelling blade III is provided with a raised rib ll along its inner lengthwise edge, the

inner wall of which is soj'jcurved as to merge into the adjacent partof the flat front face of the blade; The propelling blades are made of Ni- "hard, or some other similar alloy, having a high degree of resistance to the severe friction action of the abrasive travelling lengthwise of the same due to centrifugal force, or such face may be providedwith an impact plate of resistant:v material,

.4 the'face may be" suitabLv treated to make it resistant. Propelling blades made of Ni-hard or similar alloy are satisfactory in commercial oper. ations. Each propelling blade is provided at the opposite ends of its inner lengthwise edge with extensions i2 having reverselybeveled surfaces.

I'hat'at the outer end of the blade is comple mental to the undercut wall-8 and that'atthe inner end of theblade-is complemental to the bevel end or a flan 1" arranged peripherally of a cup shaped member i4 of an impeller element having blades I! to bedescribedl- The cup l4 its open end portion fitting snugly wfthin the axial opening of'disk l. Notchesli in the end face'of the cup-shaped member 14 receive the heads of screws 4 to provide adriving connection between the cup and shaft 3. A bolt I! extendingthro'ugh'the bottom of the cup with its shank in threaded engagement with-a tapped hole in shaft hand having its head bearing on the exterior of saidbottorn forces thefiange it into clamping Contact with theextension I! at the inner end' of the propelling blades for retaining the blades rigidly in the rotor head and for interlockingnotches i8" with the heads of screws 4.

The bottom of the cup 14 must not be so long as to contact the ring I" as: it would prevent locking engagement of flange ll against tensions II of the: blades.

The rib II at the inner lengthwise edge of each blade, is spaced ashort distance f'rom the extreme edge of the latter, and preferably interiits in a rabbet it along one edge offthe slot l in disk 0, which receives-the blade. An a'rm'lf extending from the rear face of each blade midway ofits length has an end contacting the exposedface of the disk]! to act as a brace for the blade. j I

The abrasive supply spout includes an upper section II and a lower section 2 2 The lower section-.22 is rigid with a supportin i late II bolted to the adiacent' side" wall 24 of a suitable casing which does not function as an abrasive assisting device ordevice fromwhich alarge' belied out as indicated in dotted lines to receive the abrasive from a suitable source. V The gravity head of the abrasive supply is sufflcient forlnsurlngthat the desired'quantity of s u t ia e inafo Pa sa e i the impellerjand pass lengthwi e thereof to be picked up by the innerm'arginaledges c: the blades the inner exthen the width of the propeller blade and so cated that a vertical plane transverse to the axis 3 of the rotor will substantiallyintersect the middle of the longer axis of the opening 21 and the middle of the shorter axis of the face of the propeller blade. One end wall 23 of the shell 26 has a central opening which receives the closed end portion -of the cup l4, and the opposite end wall 29 of the shell is provided with anopening which receives a boss 30 snugly fitting therein and which projects from'the inne'r'wall of the plate 23: The plate 23 is dished at and is provided at its open end with an outwardly extending flange 32 provided with openings to receive the shanks of bolts 33 which'flxedly securethe plate 23 to the adjacent side wall 24 of the casing enclosing theblasting unit. I

The end wall 23 of the shell is provided with tapped holes 35 forreceiving the threaded ends of the shanks of bolts 38 which are provided for 'adjustably securing the shell 264:0 the plate 23.

A shim or washer 34 lies between shell "and plate 23. There are preferablyiourholes 35 equidistantly spaced from one'another in the wall 23.

For permitting of the ready circumferential adjustment of the shell 23; the bottom or end wall of" plate 23 is provided with arcu'ate slots 31 through which extend the shanks of the bolts 36;

-Ifit is not desired to readily shift the position of the opening 21 after the machine has been assembled, the arcuate slots 31 and the parts now to be described, which coact with bolts 36,may be dispensed with. In that event, diametrically opposite openings would be provided through the wall of theplate 2: whichwould register with the tapped holes 35, and through which the shanks of the tworetaining bolts 36 could be passed. The head's of the bolts, or shoulders. corresponding to the under faces of the heads would be drawn into clamping contact with the outer face "of the plate 23 when the bolts are.

screwed home, for rigidly supporting the shell from'the plate. r c I As illustrated in the accompanying drawings,

however, instead of such circular openings in the plate 23, it is provided with the diametrically opposite arcu'ate slots3'l which permit the shell I to be moved circumferentially when the bolts 38 are loosenedand to be thereaftersecured in a newv position by screwingthe bolts home. The shim 34 serves as a closure for the slots 31 to prevent the escape of abrasivethrough these slots,

For maintaining a setting of theshell which has been determined upon in respect to plate 23,

notwithstanding the parts may be disassembled for the replacement of an impeller, or otherwise, there is provided an arcuate plate 33, resting against the front face of the bottom wall of the plate 23, having an arcuate slot 39 through which passes the shank of a bolt which engages a tapped opening in the wall of plate' 23; The nut 4t threaded on'this bolt clamps against the outer desired in referencefito a vertical plane inter secting menu of the spout'sectionfl, pate face of the platelliorpreventing its accidental movement after it, has been set in a desired posi-:

, tion. rv-Theuends ofthe plate 33 coact withthe bolts 36 for maintaining the plate in a fixed position between thebolts. For the latter purpose,

circular-openings 42: areprovided throughthe plate 33 adjacent eachend thereof'for receiving the shanks oi the bolts; l a

As shown herein eachof the twobolts- 36 is provided with a" shoulder-43- spaced apart from the hexagonalJ-head-. of the bolt for clamping against the outer face oithe arcuate plate 30, and thereby firmly and fixedly holding the shell 28 on the plate.23. aByxloosening the bolts 38 and nut 4|, the shell 1 2! can be circumferentially shifted; By tightening the nut M, the arcuate plate 38 will: be retained against accidental movement, and the bolts 33 will necessa y oc-' cupy the same positions,-when.replaced after the shell has been removed-from plate 23 and replaced or a new one substituted for it as before,

and this will insure that the opening 21 will occupy the same angular or circumferential position after the parts arev re-assembled as' it did before they were disassembled. For indicating the position of the opening, a-suitable scale 44 may be placed on theexterior face of the flange 32 with-which'one of the bolts" will index. 1

The impeller includes ln addition to the cup i4 a conical ring 48 coaxial of the cup and spaced a distance apart therefrom approximately the length of the opening 2I,"and a plurality of km,

pellerv blad'esliwhich bridge'the space between the bottom wall of the cup-i4 andthe contiguous wall of the ring 44. The impeller blades or yanes II are spaced widely apart-from one another circumferentially and their inner edges are thin and are'also spaced apart from one another'to provide an unobstructed axial opening or passage; As shown,these blades are of slight width. being consider bly less in width than one-half the length of t e propeller blades. The cup i4, ring 46, and blades llare-integral with chea other and are preferably formed of a single casting.. Thefiront, or propellingface, of each impeller blade is straight and initially smooth, but in use striations, or ripples, may be formed there in by the action of the abrasive, notwithstanding the'blades aremade'of Ni -hard or 'similar 'alloy' which is highly resistant to the attrition action of the'abrasive. The shell 24 is alsojr'nade of- Nihard, or similar material, which is" highly resistant to the action of the "abrasive, and this is true also of the other parts that are 'subjectedtoattritionaction. The machine is readily ing the =-flat ring! in place by screws 4. This ring 5 is then insertedinto the axial opening of the outer disk I 'of:therotor: head. Then disk 6 isafllxed to disk 'I bythescrewsshown; Next, the-propeller blades lllare placediin'position'in the slots l in the inner disk 6 of .theirotor head; Then the impeller is placed in position with slots l6 receiving. the heads of bolts 4 and secured by the bolt I] which when screwed home also looks all of the propeller blades in place. The registration of the heads of screws 4 with, the notches It establishes the properangular-relationship between the impeller blades-l5 and propeller blades II.

The shell 28and plate 23 having assem bled with the opening 21 in the g'eneralposition assembled by fixedly Se curing the'hub 2 to the driving shaft land clamp-,

28:1: fixedly'secured to the adjacent casingv wall 24 by bolts 33. Then by means of bolts 38 the shell is given such final angular adjustment'as may be: found desirable, the nut I is then screwed home, andfinally bolts 36 are also screwed home. Assuming the opening-21 is located in about the eleven o'clock positionreference being to a cloclcdial-and that the rotor is travelling in an anti-clockwise direction at a speed approximating" 2250 R. P. M., the abrasive fed 'throughthesupply spout willflow into and lengthwise of the axial opening in the impeller, and will be picked up bythe impeller blades and propelled through opening-21in a stream moving outward and across the orbital path of the inner edge of the propeller bladesyand in a direction atan' acute angle to-the face of each propeller blade as it makes'initial contact with the stream. The inner end of the propeller bladewill cut offthe outeriportion ofthe stream, and such slug of abrasive willbepicked up by the-innerend portion of the blade and. carried along .by the blade. By centrifugal force the abrasive will be caused to movelengthwise' of the face of the blade, and after the blade has travelledthrough an arc of about 90 degrees the abrasive will commence to glide on of theouter edge of'the blade. This discharge willcontinue during the travel of the blade through a succeedingiarc of about the'same length. v I

As will be noted, each propeller blade is longer than the diameter of th impeller, and the inner edges of the former travel in a, path contiguous to the peripheryof the shell. The latter-is important for minimizing the force of the impact of the blade with the i the blade, and the velocity. acquired in its movement lengthwise of theblade. Thes two velocities may respectivelybe called tangential or angular, and centrifugal velocities., y l The machineas described, with a rotor of approximately19 inches in diameter, travelling at a speed of approximately 2250 B. vP. M., has the capacity to throw at an abrading velocity upward of 30,000'pounds of metallic abrasive 'per hour. r.

As will be observed, the principle of the operationof the machine described is such that the streamdischarged from the rotor strikes the work substantially diametrically opposite from the position where the stream from theitransfer mechanism enters the rotor. -Otherwise stated, there is 'a wide separation-of the order of" about 90 degrees-between the position (arc of movement) where the propeller blade picks up theabrasive and the position where th discharge commences of the abrasive from the outer edge of the blade, notwithstanding each blade maybe straight from end'to end and radially disposed. r

In about 90 percent of the operations in which is used the machine described, the work is located below the rotor and in consequence the abrasive fed coaxialof the'rotor must be thrown. upwardly to be pickedup successively by the. propeller blades as they passthrough an'arc almost directly above the axis of rotation of the rotor.

' It will also be noted that the abrasive enterln the axis of the rotor and which'is mechanically propelled outwardly. across the path of travel of the inner edges of the propeller blades is not obstructed at all by the carrier for the. blades, and, indeed, it is not obstructed to any consequential extent by the blades themselves. To reduce the latter practically to a knife edge, the blades are bevelled at their inner edges at 48.

This machine does not require a shroud having a wall concentric with a large part of the periphery of the rotor and contiguous to the same for arresting the abrasive discharged by theblades save as they pass through an arc of limited length and returning the abrasive within the orbit of the blades or otherwise. It is also apparent that the abrasive in this machine passes directly from the. outer edges of the propelling blades unobstructedly towards the work.

It will also be noted that not only are the inner edges of the impeller blades l5 spaced apart sufficiently to provide an unobstructed axial opening or passage of ample size toreceive the abrasive from the feed spout, but that there is awide space between the front or throwing face of each blade and the rear wall vof-the immediately preceding bladev In construction andprinciple of operation our machine is radically different from thetype of machine in which the velocity of the abrasive discharged from the periphery of the rotor is due. entirely, or in large measure, to the force generated by the collision of a substantially radially disposed batter surface located adjacent the periphery of the rotorwith the abrasive which is shot againstthe same, or discharged into its path from a conduit through which the abrasive travels. :In contradistinction, in a machineexhibiting our invention the rotor is ,not

' provided with narrow: passageways so shaped as to guide the abrasive against or into the path of an abruptly disposed surface, but the abrasive is picked up by the inner end portion of the blade with a low order of impact, moves lengthwise of the blade without abrupt change in direction, and finally glides ofi of its outer edge as stated; the actionv being somewhat similar to that which occurs in the game of jai alai in which, by the wide'sweep of the playersiarm, the ball is caused to travel lengthwise of the face'of the ce'staand slide off of its outer edge to travel at great velocity towards the wall of the court.

Our machine in constructionand principle 0 operation is also radically different from the type of mechanical blasting machine which has been proposed, wherein the abrasive is discharged downwardly both into and from the rotor.

, Our machine is also radically different from the type of mechanicalblasting machine in which a shroud or baille member encloses practicallyall but a small arc of the rim'of'the rotor for arresting-the abrasive discharged from the rim save at said unenclosed portion of the rim.

Our machine is a centrifugal blasting machine in which the means for effecting directional control, or adjustable directional control, is incorporated in the machine itself, and such means includes a transfer mechanism interposed between a stationary abrasive supply spout and the rotor a short am, will glide endwise or the blades withe out material abrupt changein direction, and will invention which we desire to patent are particularly set forth in the appended claims.

We claim: I

1. In a centrifugal blasting machine and in combination, a rotor comprising a head and thin, substantially oblong: shape, propelling blades, said head comprising inner and outer disks attached to each other and of substantially the same diameter and each provided with an axial opening, that in the outer disk being of smaller diameter than the opening in theirmer disk, a driving shaft, a hub carried thereby and attached to the outer disk and provided with a circular protuberance fitting withinthe axial opening in the outer disk, said inner disk being providedwith' a radial groove opening out at one end through the wall of its axial opening and'terminating at its opposite end adjacent its periphery in an undercut end wall, projections at the opposite ends of one lengthwise edge of each propeller blade, the marginal portion of said lengthwise edge being detachably held in said groove and the projection at the outer end of the blade interfitting with the undercut end wall of the groove, a cup shape member arranged coaxial of the rotor having a marginal edgeportionfltting within the axial opening in the outer disk and having a peripheral flange cooperating with the proiection at the inner side of the blade, a bolt for drawing the cup toward the hub and the peripheral flange in clamping engagement with the projection at the inner edge of thepropelling blade, a plurality of impeller blades supported at corresponding ends by, saidqcup with their lengthwise edges spaced from one another to provide an unobstructed axial opening, a supply spout having a discharge outlet registering with the axial opening, a plate carrying the spout, a casing wall to which the plate is attached, a container having a cylindrical wall with its outer surface contiguous the orbit of the inner ends of the propeller blades and its inner surface COIL- tiguous the orbit of the outer edges of the impeller blades, said peripheral wall having a discharge opening therethrough, the ends of which are between spaced apart planes parallel with the longer edges of the propeller blades and intersecting said blades a distance within said edges, said container having an end wall with an axial opening receiving the closed end of the cup shape member and an opposite end wall provided with an axial opening, means for supporting said container from said plate including an axial boss on the plate fitting within the axial opening in the last named end wall of the container, said wall having spaced apart tapped openings therein and the said plate havingarcuate slots for registration with said openings, and bolts having their shanks extending through the arcuate slots and engaging the tapped openings and their heads in 5 clamping engagement with the outer face of the plate j 2. A cup member providedwitha peripheral flange for clamping apropeller blade of ablast; ing machine in. the carriertherefor, and a plurality ofradially disposed impeller blades; sup ported by the saidmember, the inner edges of the impeller blades beingparallel tolan axiscoextensive' with the axis of the cup and spaced apart to provide s opening. a Y

3. A cup member provided-with a peripheral flange for clamping a propeller blade of a blasting, machine in the carrier therefor," said member having a substantially flat bottom wall, and a plurality or: radially disposed impeller, blades supported by the said member and extending from said Well, thel'inner edges of the impeller blades being parallel to an axis coextei'isive with the axis of the cup and spaced apart ;t0..pro-' vide an unobstructed abrasive receiving opening, and a conical, d integral with the .ends' of the blades oppositeto the bottom-walL,

. l 4. In acentrifugal abrading machine, ia'rotor having a plurality of abrasive propelling blades provided thereon, said blades being disposed substantially radially and terminating short of the "axis of said rotor to jdeilne a central abrasive,-

admitting space, an abrasive impeller, axially aligned with said rotor'and'secured thereto, said impellerrbelng disposed within said central'space and comprisingra pair of side'jwall elements joined by e a plurality of substantially r'adial abrasiveimpelling vanes which terminate short of said axis, one of said side wall elements being of hollow formation and extending' for a considerable axial distance away from said rotor. to define an abrasive conduit,means for feeding abrasive to said conduit, and a shield device dis:

a ing' a discharge opening therein disposed to one posed between said impeller vanes and said propelling blades for directing abrasive from said impeller vanes to a predetermined angular region of said propelling blades. e e,

5. The abrading machine described in claim '4, wherein the internal surface of the conduit aefined by said side wall element inclines toward said rotor and communicateswith the'spaces be- :tween said'vanes. 7

6. The abrading machine described in claim f4, wherein said. means for feeding abras'ivecomprises a pipe telescoped into the conduit provided by said side wall element.

7. In a centrifugal blasting machine, a roto.

having a plurality of substantially radially dis-- posed blades provided thereon, said blades terminating short of the axis of said rotor, a substantially cylindrical abrasive feeding device of an external diameter less than the radius of the rotor positioned coaxially of said rotor and havside of the axis of said rotor and located between the planes of rotation defined by the sides of said blades for delivering, abrasive to the inner ends of said blades, said blades terminatingsufficiently close to said feeding device to pick up the abrasive with a minimum impact and said blades having substantially smooth and uninterrupted abrasive-propelling surfaces of sumcient length to accelerate the abrasive smoothly and continuously and without abrupt change from the point of pick-up thereof by each blade to its outer edge and discharge it therefrom at an abrading velocity when said rotoris rotated at optimum speed, a rotatable impeller comprising a plurality of impeller vanes disposed within said an unobstructed; abrasive receive feeding device, said vanes extending to a region and-dischar e it from-the outer ends of said closely adJacent the axis to define 'a comparatively small axially extending passage, and means for introducing abrasive into said passage and over the inner edges of said vanes, said vanes being operable to impel abrasive throughsaid discharge p i g;

' 8. In a centrifugal blasting machine; a rotor having a' plurality ,of substantially radially disposed propeller bladesprovided thereon,"said blades terminating short of the'axis of said rotor,

i an abrasive feeding .device positioned coaxially of'said rotor and havinga, discharge opening therein to one side vofftheaxis of said rotorand located between the planes'of' rotation defined by the sides of said blades m delivering abrasive jtb the inner ends of said blades, rotatable" means disposed in said feeding device for impelling abrasive 'throug'h said discharge opening, said ,means comprisingamplurality of impellingvanes connected to said; .rotor, said vanes being disposed substantially radially and extending inwardly to a region closely "adjacent the axis to define a comparatively small, axially disposed passage, and means iorf'introducing abrasive into said paasage andover the inner edges of said vanes, said propeller blades terminating sufliciently close to said feeding device to pickup the-abrasive 'with a minimum'impact and said blade having substantially smooth and uninterrupted abrasive propellingsurfaces of a length which is a plurality of timesgreater than thatof thewidth. of saidimpelling vanesto accelerate said'abrasivesmoothly and continuously without abrupt change initsgeneral direction of travel nating sufliciently close to said feeding. device and the axis of the rotor to pick up the abrasive with a low impact and said blades having subdevice, said impeller including spaced side wall blades for delivering abrasive across the orbit of the inner ends of said blades, said blades termiportions having a plurality of impeller vanes disposed therebetween 'said vanes extending to a region adjacent to and spaced from the axis to. define an unobstructed axially extending passage,

and means for introducing abrasive into said passage and over the inner edges of said vanes,

said vanes being operable to impel abrasivethrough said discharge opening and said side wall portions being operable todirect the abrasive throughsaid discharge opening.

'10. In a centrifugal blasting machine and in combination, a rotor, an 'brasive supply with "a discharge port coaxial the axis of the rotor and an interposed axially disposed transfer mechanism supplying the abrasive to the rotor and controlling the arc of discharge of the abrasive stream'from the periphery thereof, said rotor comprising a head and a plurality of thin, widely separated, independently functioning blades, with the spaces therebetween free for the outward travel of the abrasive stream from'the transfer mechanism across the orbit of the inner edges of the rotor blades, each rotor blade having'its propelling face highly resistant to abrasion, without material abrupt change in direction, and extending substantially from the inner edge to the outer edge of the blade, the latter edge of the blade terminating at or adjacent the periphery of the head and said inner edge thereof terminating in close juxtaposition to the transfer mechanism, and each blade in radial length ex,- ceeding the radius of the outer member of the latter,.said transfer mechanism including a multi-bladed, axial passage,'impeller and an outer member determining the position of the arc of pick-up by the inner ends of the rotor blades of theabrasive propelled by the impeller.

1 f WILLIAM A. ROSENBERGER.

WALTER L. KEEPER. 

